1. Field of the Invention
The present invention relates to a tubular anchor such as, e.g., a roof bolt, used primarily in mine and/or tunnel construction and including a tubular member having a drilling head at one of its end, load application means at its other opposite end, at least one outlet opening provided in a region of the drilling head, and filled, at least partially, with one- or multicomponent mortar mass.
2. Description of the Prior Art
Tubular anchors of the type described above are generally known. They function primarily for stabilizing walls of hollow spaces such tunnels, galleries and the like. They are used primarily for securing to each other following each other, in a direction transverse to the wall, the wall-forming strata. In many cases, the mechanical characteristics of the layers, which like in immediate vicinity of the wall surface, in particular, their supporting resistance, changes as a result of formation of a hollow space. Therefor, these layers need be secured to further located undamaged or unaffected layers or strata.
A tubular anchor or a roof bolt of the above-described type is disclosed, e.g. in U.S. Pat. No. 4,055,051. The U.S. Patent discloses a roof bolt that is formed of a tubular element provided, at one of its end, with a drilling head and, at its opposite end, with load application means. The interior of the disclosed roof bolt is partially filled with mortar mass. An exit channel extends through the drilling head. The setting process of the disclosed roof bolt is elected in two steps. In the first step, the roof bolt forms, with the use of an available drilling too, a bore in the constructional component, in particular, in the ground. The drilled-of and commutated stone, which is produced upon drilling with the drilling head of the roof bolt, is removed through outlet openings provided in the drilling head and the space between the bore wall and the outer surface of the fastening element. In a second step, a piston, which is provided at an end of the roof bolt facing in the direction opposite to the setting direction, is advanced in the setting direction, pressing out the mortar mass, which fills the interior of the roof bolt, through the openings provided in the drilling head.
A drawback of the disclosed roof bolt consists in that a convenient handling and the reliability of the mortar mass, which is located in the roof bolt, cannot be always insured. Somewhat aggressive components of the mortar mass such as, e.g., amino-based, epoxy hardener can adhere to the inner elements of the roof bolt and, thereby, adversely affect its functioning.
Further, in the roof bolt of U.S. Pat. No. 4,055,051, complete squeezing of the mortar mass out of the tubular member, is not insured as the squeezing depends to a great extent on the setting tool used for setting the roof bolt. Therefore, it is, e.g. very difficult to determine the necessary amount of the mortar mass. This circumstance is further aggravated by the fact that the costs of the mortar mass form a substantial portion of the entire costs of the roof bolt.
Accordingly, an object of the present invention is to provide a tubular anchor in which almost complete extrusion of the mortar mass out is insured.
Another object of the present invention is to provide a tubular anchor which can be economically produced and which is easy to handle.
These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing, in the tubular member, at least one, substantially cylindrical, hollow element for receiving a mortar mass and two pistons for closing the receiving element at its opposite ends and displaceable along the tubular member. The at least one receiving element has, at its end facing in a setting direction, a piston-receiving region for receiving the piston located at the facing in the setting direction end of the at least one receiving element and having at least one through-opening spaced from a free end of the piston-receiving region by a distance corresponding at least to a length of the piston received therein and measured in a longitudinal direction of the tubular member.
A pressure, which is applied from outside in the setting direction, displaces the mortar mass, which fills the space between the pistons in the mortar mass receiving element, in the setting direction. As the mortar mass-receiving element has a piston-receiving space, the piston, which is located at the facing in the setting direction end of the mortar mass-receiving means, can be displaced until it frees the through-opening providing in the piston-receiving region. The use of a sealing piston insures that the through-opening becomes open, with the application of a sufficiently high pressure, under any conditions. The tubular anchor according to the present invention can be economically produced because the manufacturing and assembly of a complicated mechanism of freeing the through-opening is not any more necessary. Storing of the mortar mass in a mortar mass-receiving element between two pistons insures a simple and reliable handling of the tubular anchor and, in particular, the handling of mortar mass. The pistons insure sealing of the mortar mass-receiving element and, thereby, storing of the mortar mass-receiving element, together with mortar mass, separately from the anchor. The receiving element can be inserted in the tubular anchor immediately before setting of the anchor. Thereby, the storage costs can be reduced, and a careful handling of the mortar mass is insured. Preferably, the-piston-receiving region has at least two through-opening uniformly distributed over a circumference of the piston-receiving region. This insures a uniform distribution of the mortar mass over the circumference of the anchor which permits the anchor to withstand increased load values. Advantageously, the drilling head has a diameter larger than a largest diameter of the tubular member. This insures formation of an annular slot in which a mixture of the mortar mass with drillings is received.
The outer diameter of the mortar mass-receiving element is preferably smaller than the inner diameter of the tubular member. This insures an easy insertion of the receiving element into the tubular member. Such design of the receiving element insures economical manufacture of the anchor. There is no need in additional elements or step for forming a channel between the tubular member of the receiving element. The foregoing insures an easy and reliable handling of the anchor. To insure placing of the mortar mass in the receiving means and to further simplify handling of the anchor, there is provided a hose-like bag for storing the mortar mass.
Advantageously, severally substantially hollow receiving elements are provided for placing the mortar mass into the tubular body. This permits to obtained a desired mixing ratio, when a multicomponent mortar mass is used, by selecting appropriate geometrical configurations of the receiving elements. In addition, a wall-free separation of separate components arranged one after another is insured. The use of several mortar mass receiving elements also facilitate storage of separate components of a multicomponent mortar mass.
Preferably, the several mortar mass-receiving elements are arranged one after another in the longitudinal direction of the tubular member. The annular cross-section of the receiving elements provides for convenient sealing of the element with appropriate sealing pistons. The arrangement of several mortar mass-receiving elements having annular cross-section one after another permits to avoid the use of additional relatively expensive elements or sealing solutions which do not insure a satisfactory sealing of the mortar mass-receiving elements.
According to the present invention each of the mortar mass-receiving elements is closed, at its opposite ends with respective pistons, with pistons, which are provided at ends of respective elements facing in the direction opposite the setting direction, being connected with each other. The adjacent pistons can be connected, e.g., by a one-piece piston rod. This permits to apply a uniform pressure to mortar mass components located in separate mortar mass-receiving elements during squeezing of the mortar mass out of the anchor. The mixing ratio of the separate components can be easily predetermined by selecting appropriate diameters of the mortar mass-receiving elements.
Advantageously, the mortar mass-receiving element or elements and the sealing pistons are formed of plastic materials. This permits to prevent deterioration of chemicals contained in a mortar mass. The chemicals come into contact with the mortar mass-receiving elements and the pistons, in particular, during the setting process.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.